There are many types of hydraulic oil pumps with different models, but there are five main leakage points, namely the seal between the sleeve and the shaft, the seal between the dynamic ring and the sleeve; the seal between the dynamic and static rings, and the seal between the static ring and the static ring seat. The seal between the sealing end cover and the pump body.

Generally speaking, the leakage between the shafts extending out of the sleeve and between the sealing end cover and the pump body is relatively easy to find and solve, but it requires careful observation, especially when the working medium is liquefied gas or high-pressure, toxic and harmful gas, which is relatively difficult. The rest of the leakage is difficult to distinguish and judge intuitively. It is necessary to observe, analyze and judge the leakage symptoms based on long-term management and maintenance practices to draw a correct conclusion.

1. Leakage during static test during installation

After the hydraulic oil pump is installed and debugged, it is generally necessary to conduct a static test to observe the leakage of the hydraulic oil pump. If the leakage of the hydraulic oil pump is small, it is mostly due to problems with the dynamic ring or static ring seal: When the leakage of the hydraulic oil pump is large, it indicates that there is a problem between the dynamic and static ring friction pairs. After initially observing the leakage of the hydraulic oil pump and judging the leakage location, run the hydraulic pump for observation. If the leakage of the wave pressure oil pump does not change significantly, there is a problem with the static and dynamic ring seals: If the leakage of the hydraulic oil pump changes significantly during operation, it can be determined that there is a problem with the dynamic and static ring friction pairs; if the leakage medium is sprayed along the axial direction, there are mostly problems with the dynamic ring seal. If the leakage medium sprays around or leaks from the water cooling hole, it is mostly due to the failure of the static ring seal. In addition, leakage channels can also exist at the same time, but generally there is a primary and secondary difference. As long as you observe carefully and are familiar with the structure, you can make a correct judgment.

2. Leakage during trial operation

After the hydraulic oil pump has been statically tested, the centrifugal force generated by the high-speed rotation during operation will inhibit the leakage of the medium. Therefore, after excluding the failure of the shaft and end cover seals, the leakage of the hydraulic oil pump during the trial operation is basically caused by the damage of the dynamic and static ring friction pairs.

The main factors causing the failure of the friction pair seal are:

①During operation, due to abnormal phenomena such as vacuuming, cavitation, and pressure holding, a large axial force is caused, causing the dynamic and static ring contact surfaces to separate; when installing the hydraulic oil pump, the compression is too large, resulting in serious wear and scratches on the friction pair end faces;

②The dynamic ring seal is too tight, and the spring cannot adjust the axial floating amount of the dynamic ring;

③The static ring seal is too loose, and when the dynamic ring floats axially, the static ring is separated from the static ring seat;

④There are granular substances in the working medium, which enter the friction pair during operation, and the dynamic and static ring seal end faces are inspected;

⑤The design and selection of the wave pressure oil pump is incorrect, the sealing end face pressure is low or the sealing material has a large cold shrinkage. The above phenomenon often occurs during the trial operation of the hydraulic pump. Sometimes it can be eliminated by properly adjusting the static ring seat, but most of them need to be disassembled and replaced.

3. Sudden leakage during normal operation

The sudden leakage of the hydraulic oil pump during operation is rarely due to normal wear or has reached the end of its service life, but most of them are caused by large changes in working conditions or improper operation and maintenance.

①Evacuation, cavitation or long-term pressure holding lead to seal damage;

②The actual output of the pump is too small, a large amount of medium circulates in the pump, heat accumulates, causing the medium to gasify, resulting in seal failure:

③For a long period of shutdown, the friction pair will tear the sealing surface due to adhesion when restarting;

④The number of corrosive, polymerizing and gelling substances in the medium increases:

⑤The ambient temperature changes sharply;

⑥Frequent changes or adjustments in working conditions:

⑦Sudden power outages or shutdowns, etc. If the hydraulic oil pump suddenly leaks during normal operation, if it is not discovered in time, it will often cause major accidents or losses. It must be taken seriously and effective measures must be taken. Note:

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